In order to increase the output and torque, but also to reduce the fuel consumption and exhaust emissions, of internal combustion engines for road vehicles, cam shaft phase setters for varying the inlet and also outlet control times have become widespread. Due to their high degree of reliability, but also in view of a favourable cost-benefit relationship, hydraulic phase setters which are operated by the lubricating oil for the combustion engine in accordance with the principle of the hydraulic pivoting motor have proven to be of value. Increased demands on fuel consumption and emissions require high setting speeds. In order to raise the setting speed, in particular at a low lubricating oil pressure and low oil temperature and a correspondingly high viscosity, EP 1 985 813 A2 provides a pressure storage means in the lubricating oil supply of the phase setter, wherein said pressure storage means ensures a sufficiently high setting pressure for the phase setter, even in operational situations of the combustion engine which are problematic with respect to the hydraulic supply.
EP 0 931 912 B1 provides a valve control comprising a cam shaft and hydraulic force transmission and, for the force transmission, a pressure storage means comprising a storage chamber and a spring member which is arranged in the storage chamber and tensed by the oil pressure when the combustion engine is in operation and held, when tensed, in a positive fit by means of a blocking circuit. When the combustion engine is started, the stop means of the pressure storage means is automatically released, and the spring member relaxes, thus discharging the pressure storage means in the direction of the cam shaft hydraulic force transmission until it has again reached its discharged state. This ensures that a fluid pressure required for the valve control is provided, even when starting the combustion engine.
In accordance with WO 2009/027178 A1, by contrast, a pressure storage means is attuned to the pressure which prevails in the lubricating oil system, such that it is already completely filled with the oil when the hot idling pressure is reached. The “hot idling pressure” usually refers to the oil pressure which prevails in the oil system at the idling rotational speed in the hot operational state of the combustion engine. This configuration is intended to ensure that a locking engagement, which blocks an adjustment of the rotational angular position of the cam shaft relative to the crankshaft, can be released even when the combustion engine is idling. By contrast, WO 2009/089984 A1 proposes selecting a minimum response pressure of the locking means which is greater than a minimum response pressure of the pressure storage means. The pressure storage means should however still be completely filled with the oil at the hot idling pressure. The intention is to prevent the locking means from being unlocked during the starting phase or in idling phases of the combustion engine.
While the pressure storage means known from EP 0 931 912 B1 is configured to the hydraulic supply immediately as the combustion engine is started, by conserving a high pressure from the operation at a high rotational speed from an earlier operational phase of the combustion engine, the pressure storage means of WO 2009/027178 A1 and WO 2009/089984 A1 are only suitable for absorbing pressure spikes in the starting phase and at most in idling phases of the combustion engine.